I read the first few pages only, so my apologies where I have duplicated the ideas of others. My comments relate to established congregations; church-plants should be supported initially by other existing congregations (as was the practice among the apostles), not by the new one.
Clearly, there is no set number, either in Scripture or practice. There are a few things to consider, but I believe that the most important is expectations: what the church expects the pastor to be (qualifications) and do (responsibilities).
A pastor in a rural village in Malaysia may not need a car; a pastor in rural Texas probably does. A pastor in Inuvik may need a snowmobile, while one in Fiji may need a boat. Each will need food, shelter and clothing. A single pastor with no children doesn't need what a married pastor with five kids needs. At the same time, the single pastor should not be paid less simply because of a choice to remain single; payment should be according to the job requirements, with the consideration of the cost of living in that area.
If a church requires that its pastor be educated, they need to pay for that. If they require an advanced degree, they need to up the ante. If they want a high-capacity person who could easily earn $100,000 in the marketplace, they should expect to pay $100,000. If they are content with a two-year Bible school certificate, the job requirements should reflect that as much as the salary should.
Balance these expectations with the ability of the local congregation: rural Appalachia likely isn't going to pay any pastor even $40,000. They should expect to pay enough that the pastor can live in the same area and attend to required duties, which probably include travel expenses. As with any job, the worker should not be out-of-pocket to fulfill it.
Set aside what the pastor feels called to do. Paul did not take a salary, but he made it clear that those working for the gospel should earn their living from the gospel. What a pastor is willing to accept should not have bearing on what the congregation "should" pay. Further, the life decisions of the pastor are not made by the congregation, so the congregation should not bear responsibility for them (previous debts, having a large family, etc.). The job pays what it pays, and ideally the generosity of individuals in the church will make up any additional need. A pastor needs to demonstrate wisdom in private affairs including finances and their use. I would add that if a congregation expects the pastor's spouse to work for the church, they should pay the spouse as well!
One final note: it's God's church; so ultimately He should be directing the disposition of finances. In other words, the board (or whoever makes such decisions) should consider all these things with much prayer, and actively seek divine guidance for the final numbers in the contract.